Pumping Iron

The flower-like
patterns are created by magnetic fields acting on the black liquid.
With the buttons and the knob, visitors tell a computer what pattern
they want to see. The computer directs pulses of electric current
through a coil, creating a magnetic liquid above it. The black liquid
is made of magnetite (iron oxide) particles suspended in a carrier
fluid. Magnetic fields attract the tiny magnetic particles, pulling
them (and the carrier fluid) up against the force of gravity. .